Recording device



March 15, 1938. 5 ENNE 2,111,231

RECORDING DEVICE Filed June 14, 1935 INVENTOR.

TTZQHIred van Qrden/Ie ATTORNEY.

Patented Mar. 15, 1938 RECORDING DEVICE Manfred von Ardennc, Berlin-Lichterfelde-Ost,

Germany, assignor to Radio Patents Corporagon, New York, N. Y., a corporation of New ork Application June 14, 1935, Serial No. 26,625 In Germany June 27, 1934 13 Claims. (Cl. 250-27.5)

This invention relates to recording devices, the intensity variations. Such displacement more particularly devices for photographic recauses frequency variations in the case of sound cording of sound and the like, and a. method of recording, resulting in undesirable distortions of operating such devices. the sound vibrations, such as speech or musical The sound. recording device as described by the sounds to be recorded. invention is constructed and operated according On the other hand, devices employing a linear to the cathode ray oscillograph principle, such source of electron emission associated with an as embodied in the well known Braun cathode electron lens system to produce an image of the ray tubes as known in the art. linear electron source upon the fluorescent screen,

A great number of special constructions of possess similar disadvantages of a displacement un tubes have b come kn wn sp ially deof the recording line together with and dependsigned for sound recording purposes- In most of ent on the variations of the light intensity. these devices a fluorescent line is produced upon Moreover, devices of this type have the further the luminous screen of the cathode ray tube, the drawback of an uneven luminosity of the lumiintensity of which is varied in, accordance with nous line caused by unavoidable irregularities of the vibrations such as sound vibrations to be rethe electron emission from different points of the corded. In one construction of a recording tube cathode surface. Extensive experiments carried of this type, the luminous line is secured by out by the inventor have proven that great difmeans of a filamentary cathode in connection flculties are encountered in securing a uniformwith a cylindrical lens which may be either an ly illuminated line of extended and constant optical lens or a lens of the electronic type. Aclength by means of a punctiform or linearly cording to another construction of recording shaped cathode and an associated cylindrical tubes of the Braun oscillograph type, the lumielectronic lens system. There are two substannous line is produced by a deflection of the cathtial defects inherent in devices of this type. In Ode y in O direction y a gh frequency the first place, the range of equal luminosity essweep potential causing a us line p pecially during the control in the direction to the fluorescent screen as is well known. Other dark value amounts to a few millimeters only, constructions of recording tubes employ diaresulting in a too narrow sound track when using phragms with a slit-like aperture and strong the customary optical reduction. In the second magnetic fields in the vicinity of the fluorescent place, the length of the fluorescent line varies screen for securing a sharply defined luminous dependent on the intensity within wide limits. recording line. Thus for instance, the length of equal luminos- The above and further constructions known in ity during the control to bright values amounts the art possess various disadvantages especially to about five to ten times the above mentioned when designed for recording sound such as for length during the control to dark values. This use in the talking moving picture and similar amplitude modulation is highly undesirable as it arts. These disadvantages consist primarily in leads to uncontrollable conditions and distora poor quality of the sound record, low light intions in sound recording. tensity, the necessity of high controlling poten- The above mentioned Variations of the length tials, short life of the tube, lack of constancy" of the luminous line dependent on the controlof operating characteristics and. difficulties in adling signal intensity are primarily due to the fact justment and attendance. Thus for instance, that in the usual construction of the tubes the diwhen employing deflection of the cathode ray in verging angle of the electrons emitted from the one direction at high frequency as mentioned cathode varies dependent on the potential applied above, the end portions of the recording line to the control electrode. The control is usually have a higher intensity due to the longer stay of effected by means of a control electrode disposed the fluorescent spot at the reversing points of close to the cathode and having a potential varythe high frequency sweep potential. This disading about a mean value, in most cases a negative vantage may be eliminated by screening off the potential, in a manner similar to the grid elecend portions of the recording line, with the re-- trode in known vacuum tube amplifiers used in sult of a substantial loss of light or, if no screen radio and allied arts. The divergent angle of the is used, of a decrease of the possible efiective conelectrons emitted from the cathode decreases with trol range. Moreover, tubes containing a gas increasing negative potential of the control elecfllling have the disadvantage that a displacement trode, and vice versa the divergent angle increases of the fluorescent line occurs simultaneously with with decreasing negative potential of the controlling electrode. This undesired variation of the divergent angle of the electrons leaving the cathode in tubes employing a cylindrical electron lens system can be eliminated by providing a suitably constructed control electrode arranged and oriented in such a manner that divergence occurs only in a direction at right angle to the light slit in the control electrode and is substantially prevented in a direction parallel to the light slit in the control electrode. This effect can be obtained practically by using a filamentary cathode and by constructing the control element in the form of plate electrodes disposed at both sides of the cathode filament. By a proper design of the shape or marginal curves of these plates and also by using cathodes curved in a direction towards the electron lens system, it is possible to diminish the variations of the divergent angle to a substantial degree.

An object of the present invention is to provide a simple construction of a recording tube of the Braun oscillograph type for producing a fluorescent line of extended length and substantially uniform intensity. Other objects and aspects of the invention will be apparent hereafter from the detailed description thereof in connection with the accompanying drawing in which I have shown one embodiment of a recording tube constructed in accordance with the principles of the invention.

Fig. 1 of the drawing shows the recording tube in cross-section,

Figs. 2a to 2d represent side views of the sepa rate electrodes taken on line aa to d-d.

Figs. 3 and 4 are front and side elevational fractional views showing a modified electrode construction for a tube according to Fig. 1.

Similar reference numerals identify similar parts. 7

Referring to the drawing, I have shown at I an evacuated vessel or container such as a glass bulb of suitable size and shape having a reentrant stem 2 and a pair of mounting rods 3 for supporting the separate electrodes within the tube. The electrons emitted from a suitable source such as the cathode 4 which may be an indirectly heated cathode of known construction, are passed through the small slit M of a control electrode shown at 6 disposed in close vicinity to the cathode and being of a curved or arcuate shape and having its concave side directed towards the cathode as shown. This electrode is connected to an outside terminal 6' through a suitable lead wire passed through the stem 2 of the tube and in operation is suitably biased by a' negative potential and connected to the source of controlling current variations, such as the output circuit of a microphone orsimilar device producing electric current or potential variations narrow slot l5 substantially parallel to the slot M of the control electrode 6 and being also of curved or arcuate shape as shown with its concave side directed towards the cathode. The electrode 8 which serves as a first acceleration electrode is connected to another outside lead shown at 8 similar to the control electrode 6 and in operation is connected to a source of positive potential of several hundred volts in such a manner as to secure a sharply defined line upon the luminous screen l3 at the opposite end of the tube by the conjoint action of the cylindrical electron lens system to be described presently. The special shape of the first pre-acceleration electrode 8 as described has the effect that the lines of the electric field which the electrons have to follow after leaving the cathode assume strongly divergent directions. This divergence of the field lines is independent of the potential applied to the control electrode and in the case of a tube of the approximate dimensions as shown is sufficient to cause the opening of the cylindrical electron lens formed by the electrodes 9 and II to be evenly and uniformly irradiated by the electron pencil. Experiments have proven this fact and shown that the diverging angle is substantially independent of the varying intensity of the electron pencil.

According to a further feature of the invention, the cathode is preferably provided with a uniformly heated flat emitting surface evenly covered with a suitable oxide or other electronically active material as indicated in the drawing. At the edges the distance of the negatively biased control electrode from the emission surface is less than in the middle due to the curvature of the control electrode, resulting in a greater effect of the accelerating field and increased electron emission at these regions. In this manner the end regions of the light line which otherwise would have a lesser luminosity will have substantial equal light intensity as the remaining portions of the line. The small distance of the control electrode from the cathode insures a high mutual conductance of the characteristic control curve thus making it possible to operate a tube of this type with very low controlling potentials of a few volts only.

The part of the electrode system described heretofore serves to produce an electron pencil of linear cross-section and of equal and uniform intensity impinged upon the electron lens system independently of the intensity variations in accordance with the controlling signal variations.

The cylindrical electron lens system in the example shown is comprised of the two further substantially disc shaped electrodes 9 and II arranged parallel to the electrodes 6 and 8. The electrode 9 mounted at the side of the electron source is provided with a slit I6 01' a larger width than the slit ll of the final acceleration electrode I I mounted at the side of the fluorescent screen I3. In order to simplify the construction of the tube, the acceleration electrode 8 and the electrode 9 are conductively connected, as shown.

However, it is understood that these electrodes may be provided with separate leads and separately and differently biased to suit any special requirements. The high tension anode voltage which in the case of present day sound recording devices of this type amounts to about 1500-2000 volts is applied to the final acceleration electrode II which is shown connected to an outside terminal lead I I. The cylindrical electron lens system shown is constructed in accordance with an electrostatic acceleration lens. It is understood, however, that any other electron lens system or combinations of electronic lenses may be provided for practicing this invention. The image formed on the fluorescent screen corresponds to the slit of the first acceleration electrode 8.

I have shown in Figs. 3 and 4 a modified practical form of an electrode construction for a tube as described in Fig. 1 comprising a set of concentric cylindrical electrodes in place of the fiat electrodes shown by Fig. 1. Item 22 represents a cylindrical cathode of known construction concentrically surrounded by a cylindrical control electrode having a horizontal slot 21 and serving a similar purpose as the electrode 5 according to Fig. 1. The remaining cylindrical electrodes 24, 25 and 26 provided with horizontal slots 28, 29 and 3E], respectively, in register with the slot 2! correspond to the electrodes 8, 9 and II as shown by Fig. l and it is understood that the same effect of a radially divergent electric field is obtained with an electrode construction of this type for the object and purpose in accordance with the novel principle of this invention.

Practical experiments made with a recording tube of the type described have proven its high sensitivity and substantial independence of the length of the luminous line on the controlling light intensity as well as a complete elimination of the displacement of the luminous line which may have an extremely narrow width (in the case of dimensions corresponding to those shown in the drawing about of a millimeter). As a result of this, the luminosity is increased to such values that despite the losses in the associated lens systems arranged outside the tube less sensitive photographic emulsions may be successfully used for sound recording than was heretofore possible in the art.

While I have described my invention in its preferred embodiment, I desire it to be understood that modifications and variations may be made and that no limitations upon the invention are intended than are imposed by the scope of the appended claims.

I claim:

1. A recording device comprising an evacuated vessel, a cathode therein, a control electrode having a slit therein disposed opposite said cathode for producing an electron pencil of linear crosssection, a fluorescent screen impinged by said electron pencil, an acceleration electrode disposed close to said first electrode having a curved shape with its concave side directed toward said cathode, said acceleration electrode having a slit parallel to said first slit for passing said electron pencil.

2. A recording device comprising an evacuated vessel, a cathode therein having a flat electron emitting surface, a control electrode of curved shape and having a slit disposed close to said cathode with its concave side directed toward said cathode for producing an electron pencil of linear cross-section, a fluorescent screen impinged by said electron pencil, and means for accelerating said pencil towards said screen in uniformly diverging directions from said cathode.

3. A recording device comprising an evacuated vessel, a cathode therein having a flat electron emitting surface, a control electrode of curved shape having a slit disposed close to said cathode with its concave side directed towards said cathode, a fluorescent screen opposite said cathode, a first acceleration electrode disposed close to said control electrode having curved shape and arranged substantially parallel to said control electrode, said acceleration electrode being provided with a slit in line with said first slit, final acceleration means close to said screen.

4. In a cathode ray device, the combination of a source of electrons, an accelerating electrode disposed close to that source and having a curved fan shaped electron pencil, and a luminescent screen impinged by said electron pencil.

5. In a cathode ray device, the combination of a source of electrons, an accelerating electrode disposed close to and in line with said source and having an arcuate shape with its concave side directed towards said source, said electrode having a slit to produce a fan shaped electron pencil and a luminescent screen impinged by said elec tron pencil.

6. A recording device comprising an evacuated vessel, a cathode therein having a flat electron emitting surface, a control electrode of curved shape having a slit and disposed opposite said cathode with its concave side directed towards said cathode, a fluorescent screen, a first acceleration electrode having a curved shape and disposed opposite and parallel to said control electrode, said acceleration electrode having a slit in line with said first slit, and an electronlens and final acceleration means between said first acceleration electrode and said screen.

7. A recording device comprising an evacuated vessel, a cathode therein having a flat electron emitting surface, a control electrode of curved shape having a slit and disposed close to said cathode with its concave side directed towards said cathode, a fluorescent screen opposite said cathode, a first acceleration electrode having a curved shape and disposed opposite and parallel said control electrode, said acceleration electrode having a slit in line with said first slit, and an electron lens and final acceleration means comprising a pair of plates disposed between said first acceleration electrode and said screen, each of said plates having a slit in line with said first slits.

8. A recording device comprising an evacuated vessel, a cathode therein having a flat electron emitting surface, a control electrode of curved shape having a slit and disposed opposite to said cathode with its concave side directed towards said cathode, a fluorescent screen, an initial acceleration electrode of curved shape disposed opposite and parallel to said control electrode, said acceleration electrode having a slit in line with said first slit, and an electron lens and final acceleration means comprising a pair of acceleration electrodes disposed between said initial acceleration electrode and said screen, said final acceleration electrodes being provided with slits in line with said first mentioned slits, the slit in the final acceleration electrode close to said screen having a smaller Width than the slit in the final acceleration electrode close to said initial acceleration electrode, and a conductive connection between said initial acceleration electrode and the final acceleration electrode adjacent to it.

9. In a device of the characted described, an evacuated vessel, a source of electrons therein, means for initially concentrating the electrons emitted from said source into a flat fan shaped pencil of substantially uniform density diverging from said source, a fluorescent screen impinged by said electron pencil and electron-optical focusing arrangement comprising a pair of final acceleration electrodes disposed between said initial concentrating means and said screen and having slits in line with each other for passing said electron pencil, the slit of the acceleration electrode at the side of said screen having a lesser width than the slit of the acceleration electrode at the side of said initial concentrating means, thereby to define a luminous line of predetermined narrow width upon said screen.

10. In a device of the character described, an evacuated vessel, a source of electrons therein, an arcuate initial acceleration electrode adapted to produce a divergent field for initially accelerating and forming electrons emitted from said source into a fiat fan shaped pencil of substantially uniform density, a luminescent screen arranged for impingement by the electron pencil, and an electron-optical focusing arrangement comprising a pair of final acceleration electrodes arranged between said initial acceleration electrode and said screen and having slits arranged to pass said electron pencil, the slit in the final acceleration electrode at the side of said screen having a lesser width than the slit in the final acceleration electrode at the side of said initial acceleration electrode, thereby to define a luminous line of predetermined narrow width upon said screen.

11. In a cathode ray device, an evacuated vessel, a cathode stream source therein, an initial electrode adapted to produce an acceleration field uniformly spreading the cathode stream from said source in divergent directions, means for segregating a fiat fan shaped electron pencil from the electron stream accelerated by said field, a luminescent screen arranged for impingement by said electron pencil, and an electron-optical focusing arrangement disposed between said segregated means and said screen comprising a pair of final acceleration electrodes having slits arranged to pass said electron pencil, the slit in the final acceleration electrode at the side of said screen being of lesser width than the slit in the final acceleration electrode at the side of the cathode, thereby to define a luminous line of predetermined narrow width upon said luminescent screen.

12. In a cathode ray device, the combination of a source of electrons, means for initially forming electrons emitted from said source into a flat pencil of substantially uniform density, a

luminescent screen impringed by said electron 5 pencil, and an electron-optical focusing arrangement comprising a first acceleration electrode having a slit arranged for passing said electron pencil and at least one further acceleration electrode disposed behind said first acceleration electrode in the direction of the electron pencil, said further acceleration electrode having a slit in line with the slit of said first acceleration electrode and having a lesser width than the slit of said first acceleration electrode, thereby to define a luminous line of predetermined narrow width upon said screen.

13. In a cathode ray device, the combination of a source of electrons, means for initially concentrating the electrons emitted from said source into a fiat pencil of substantially uniform density, a luminous screen impinged by said pencil and an electron-optical focusing arrangement disposed between said initial concentrating means and said screen and comprising a diaphragmatic pre-acceleration electrode having a slit arranged to pass said electron pencil and a second diaphragmatic final acceleration electrode disposed behind said pre-acceleration electrode in the direction of the electron beam, said final acceleration electrode having a slit in line with said first slit and of lesser width than said first slit, thereby to define a luminous line of predetermined narrow Width upon said luminescent screen.

MAN FRED VON ARDENN E. 

